when uploading a document you’ll need to change to a multipart/form-data Content-Type
Here is a working example
curl -X POST \
http://ninja.test:8000/api/v1/clients/1YQdJ2dOGp/upload \
-H 'Content-Type: multipart/form-data'\
-H 'X-API-TOKEN: tokeytoken' \
-H 'X-Requested-With: XMLHttpRequest' \
-F _method=PUT \
-F documents=@/home/david/settings.txt;